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INAF-project: Gravitational Astrophysics
Electromagnetic follow-up of gravitational wave
candidates: perspectives in INAF
Enzo Brocato
INAF-Osservatorio Astronomico di Roma
Collaboration with
M. Branchesi, E. Palazzi, E. Pian, L. Stella
INAF (Istituto Nazionale di Astrofisica) decided to
participate in the EM follow-up program
as an Institution
by providing Italian observational resources
and the expertise in time domain astronomy
Advanced GWdetector era observing scenario
BNS system at 80 Mpc
2016-17
HLV
HLV
2017-18
HLV BNS system at 160 Mpc
HILV
2022+
Position uncertainties
with areas of tens to
hundreds of sq. degrees
2019+
 90% confidence localization areas
X  signal not confidently detected
Summary of plausible observing scenario
LSC & Virgo collaboration
arXiv:1304.0670
aLIGO/Virgo Range
Rate
Localization
3
|b|< 20 degree
The Galaxy
Photometry in
Crowded fields
Es.: RRLyrae
(Δ V < 1 mag)
Spatial resol.
PSF software
=> apparent bright source
 Small telescope with large FoV can be used
but.. Absorption by interstellar medium (NIR!)
|b| > 20 degree
Field of View: ~1’x1’
Cluster of galaxies
Spiral galaxy
Remote galaxy
=> Observational strategy
Distant object => apparent faint source
 Telescopes with large collecting areas
have to be used
but.. Large FoV are still needed !
Es. Supernovae, kilonovae, GRB
GRB short (good candidates) :
Searching for afterglows (interaction with the surrounding media)
Difference between images is the most used technique to discover
GRB afterglows => Reference images are a key tool
Image 1
GRB051227
GRB071227
Image 2
Difference 1-2
I ~ 23 mag
GRB061006
D’Avanzo et al. 2009
Other groups :
PTF - Palomar Transient Factory
8 deg
“The case of GRB 130702A demonstrates
for the first time that optical transients can
be recovered from localization areas of
∼100 deg2, reaching a crucial milestone
on the road to Advanced LIGO.”
Detection limit: R ~ 20.5
Singer et al. 2013:
“We report the discovery of the
optical afterglow of the γ-ray burst
(GRB) 130702A, identified upon
searching 71 deg2 surrounding the
Fermi Gamma-ray Burst Monitor
(GBM) localization.”
INAF: VST transient search SUDARE (Supernovae)
Processing steps (~ 24 hours) • Image Analysis is performed by
running specific pipelines.
 Observations (VST)
• The human intervention is not yet
 Data delivery (>2h)
negligible.
 Calibration
• Efforts are needed to improve and
 Search of transient
automatize these procedures and
speed up the process
 Validation
 Characterization (VLT)
How to identify uniquely the EM counterpart ?
 Comparison with template spectra
 Light curves
Botticella et al 2013
11050 transients
in 1 sq degree
9 SN detections
SUDARE@VST Cappellaro et al 2013
STEPS for an efficient EM-follow up
Wide-field telescope
FOV >1 sq.degree
• Reference Images
• Observational strategy
• Send data to Image
Analysis Server
VST
Image Analysis Server
“Fast” and “Smart”
software
to select a sample of
candidate counterparts
Candidate
characterization
VLT
LBT
The EM Counterpart of GW!
• GPU for rapid and
precise photometry
• machine learning to
identify and classify the
transients:
Thousands  a few
• Spectra vs templates
• Light Curves
• Multi-wavelength
analysis (Near-IR,
Radio, Space, ASTRI,
CTA)
INAF- project: Gravitational Astrophysics
Advisory Board
(L.Stella)
P.I.: E. Brocato
Working Groups
M. Branchesi
E. Brocato
A. Grado
E. Cappellaro
E. Pian
S. Campana
• GW
astronomy
• Contact with
LIGO / Virgo
Collaboration
• Search for EM
candidates
• Photometric
software
• Surveys,
Ref. Images
•Characterization
• Spectroscopy
• Light Curves
• Multiwavelegth
observations
• ToO proposals
• Relationship
EU partners
• Space
• Time Domain
Astronomy
• VLT
• NTT
• ESO
telescopes
• Swift
• XMM
• Chandra
• Fermi
• INTEGRAL
• GW physical
information
• EM
Observational
strategies
• Simulations
• VST
• CITE
• TORTORA
• Sicily (tbd)
• LBT
• NOT / TNG
• REM
• AZT-24 (NIR)
• SRT (Radio)
INAF: WIDE-FOV telescopes to cover the GW error box
South America
VST - 2.6 m VLT Survey ESO telescope
 corrected FOV 1 deg x 1 deg, pixel scale of 0.21”/pixel
 1 hour to cover a sky area of 40 sq. deg. in r’ band
reaching a magnitude of about 23
in 2016 the INAF-Guaranteed Time Observation
20% of the total observing VST time
 Public Surveys: Reference Images available
REM (Rapid Eye Mount): 60 cm diameter fast robotic telescope
TORTORA camera (Telescopio Ottimizzato per la
Ricerca dei Transienti Ottici RApidi) FOV 24°x32°,
time resolution 0.1 s, B-limiting magnitude 11
 two cameras can observe simultaneously in optical and
NIR (J, H e K), FOV 10x10 arcmin
INAF: WIDE-FOV telescopes to cover the GW error box
Europe
“Campo Imperatore Transient Experiment”:
60cm Schmidt telescope with a 2 sq. deg. FOV up to
V ~21mag (project to extend to 6 sq. degree)
 near-IR telescope, AZT-24 FoV of 4.4’x4.4’ for characterization
Funds to realize a 1m Telescope (FOV 8 sq. deg) in Sicily
+ SMALLER FOV telescopes like Asiago, Loiano, IRAIT can help during the
search and/or are useful for the characterization
INAF: Characterization of the EM counterparts candidates
North America
Large Binocular Telescope (Arizona)
excellent for characterization,
INAF GTO+ToO (25 % INAF)
 two 8.4 meter primary mirrors
.
 collecting area equivalent to an
11.8-meter circular aperture
 Optical/IR spectrographs
 Large Binocular Camera, FOV 23'x23' , sampling of 0.23”/pixel
South America
Very Large Telescope (VLT, ESO)
• four unit telescopes with main mirrors of 8.2m diameter
•very useful X-shooter spectrograph covering a very wide range of
wavelengths [UV to near infrared] simultaneously
INAF intends to coordinate collaborative ToO proposal
involving other European groups working in the field
INAF: Characterization of the EM counterparts candidates
Canarie
TNG (Telescopio Nazionale Galileo)
 3.58m optical/infrared telescope
 currently optimally equipped for “exoplanet search”
 its position could be crucial for the EM-follow up, (few)
possibility to set up instruments for this program
NOT (Nordic Optical Telescope 2.5 m) (+ Xshooter?)
good candidate for GW follow-up, thanks to its
good optics and versatile instruments: e.g.
ALFOSC (Andalucia Faint Object Spectrograph and Camera)
 GTO (fraction) + proposal for ToO
INAF:
Radio facilities
INAF radio antennas:
 Medicina (30 m parabolic antenna)
 Noto (32 m parabolic antenna)
 Sardinia Radio Telescope (64 m)
SMALL FOV  characterization
INAF: Space high-energy facilities
From space, INAF can guarantee access - through
submission of regular or DDT proposal starting from
coordinated initiatives of the INAF scientists - to Swift,
XMM, Chandra, Fermi, INTEGRAL.
INAF: Archival search
LBT + VST image archives
ASDC Archive of space missions + ESO data archive
INAF- project: Gravitational Astrophysics
 Large FoV (1x1 d)+ mag limits (< 23 m) + High resol. (0.2 p/”)
 Characterization: up to 8m class telescopes
 Site: southern and northern hemisphere
 Wide wavelength coverage: ground based facilities from
optical to radio + high-energy space facilities
 Know-how: Time Domain Astronomy, Observational Strategy,
Image analysis, Accurate Photometry in crowded fields, GRB
astronomy, Data Interpretation, Theoretical models
 Collaboration with Virgo teams is crucial
Thank you